CD19 and leukemia: The mechanisms associated with loss of CD19 after CART cells therapy include the deletion or mutation of CD19 gene in leukemic cells [7, 8], abnormal CD19 RNA splicing because of decreased expression of splicing factor SRSF3 [8], leukemia lineage transformation caused by transcription factors PAX5 and EBF1 associated reprogramming of the pre-B cells [9, 10].